Scott and Osborn.] ^bo [Sept. 2, 



3Ieasurements. 



M. 



Length upper molar series ? .053 



" " premolar series ? .026 



" " true molar " 027 



Length lower molar series 054 



" " premolar series 027 



" " true molar " 027 



Antero-posterior diameter, third upper molar 010 



Transverse " " " " 008 



Antero-posterior diameter, third lower molar 012 



Transverse " " " " 006 



Pi'otoreodon . {?) pumilus (Agriochoems pumilus) Marsh.* — Professor 

 Marsh has described a species of Agriochoerus from the Uinta beds, which 

 more probably belongs to Proioreodon ; but as the description given is 

 very brief and no mention is made of the very characteristic autero- 

 intermediate cusp on the upper molars, it may possibly be a member of 

 some other genus. 



Leptotragulus proavus, gen. et sp. nov.^ — This genus resembles the White 

 River form Leptomeryx, but differs from it in the somewhat less complex 

 structure of the last lower premolar, and in the presence of a strong 

 accessory column between the external cusps of the lower molars. In all 

 probability also this genus had separate metapodials, while in Leptomeryx 

 there is a cannon bone in the hind foot. Apparently the nearest ally of 

 this genus is the Pi'odremotJierium of Filhol, with which indeed it may 

 prove to be identical ; at present, however, we have judged it best to sep- 

 arate the American species, as aside from the fact that Prodremotheririm 

 has cannon-bones ia both fore and hind feet, the last lower premolar, 

 judging from Filhol's figures,! is somewhat more complex in structure, 

 and less distinctly trenchant than in Leptotragulus. The latter is at once 

 distinguished from its cotemporary Protoreodon, by the form of the mandi- 

 ble, which is very slender, with tapering chin and diastema behind the 

 canine, while in Protoreodon the mandible is deep with abruptly rounded 

 chin and no diastema ; a further difference is found in the premolar for- 

 mula of the lower jaw, four in Protoreodon, three in Leptotragulus. The 

 premolars resemble most those of the tragulines ; the last one consists of 

 a high, sharp and compressed cone, with a very small autero-internal 

 cusp, and a narrow valley on the posterior edge enclosed between two 

 thin plates of enamel ; this valley is not complicated by the accessory 

 tubercles found in Leptomeryx. 



The species L. proamis considerably exceeds in size the Leptomeryx 

 Evansi of the White River formation, and is somewhat larger than 

 Tragulus javanicus. The crowns of the lower molars are low and broad 

 in proportion to their length. 



* Am. Jour. Sci. and Arts, 3d Ser., Vol. ix, p. 250. 



t Rech. sur les Phosphorites du Querey, Figs. 265, 266. 



